• Fuel Injectors
• Injection Actuation Pressure Control Solenoid
• Ether Aid Solenoid
• Demand Fan Control Solenoid
• Flexxaire Fan Control Solenoid
The Injection Actuation Pressure (IAP) sensor (1) is installed in the left side of the cylinder head, above the fuel transfer pump. This sensor is used to determine the hydraulic (engine) oil pressure that is used to actuate the fuel injectors.
The status of the Injection Actuation Pressure (IAP) sensor may be viewed using Cat ET, or through the LCD display on the Main Display Module in the dash, using the 4C-8195 service tool.
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The Upper Speed/Timing sensor (1) and the Lower Speed/Timing sensor (2) are installed in the rear of the timing gear cover, below the HEUI pump. These two sensors are "Hall Effect" type sensors that read a timing wheel in the front gear train.
The sensor are installed with a clip and a bolt. The clearance (air gap) between the sensor and the timing wheel is preset and needs no adjustment.
The Upper (high speed) Speed/Timing Sensor (1) measures engine speeds for normal engine operations, including governing and crankshaft position for timing purposes and cylinder identification.The Upper Speed/Timing sensor is optimized for high speed operations. The timing accuracy of the Upper Speed/Timing sensor is greater at higher speed ranges than the lower sensor and is therefore the primary sensor during normal operations.
The Engine ECM shares the engine speed information with the Machine ECM for use in the AutoShift, the Auto KickDown, and other electronic power train strategies.
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The Lower Speed/Timing sensor (2) has a high output and is less accurate at high speeds than the upper sensor. The Lower Speed/Timing sensor is optimized for cranking speeds. This sensor functions as a back-up for continuous operation if the high speed sensor fails. A failure of the Upper Speed/Timing sensor will cause the Engine ECM to automatically switch to the Lower (cranking) Speed/Timing sensor. During this condition the check engine lamp will turn ON.
The status of the engine speed/timing sensors may be viewed using Cat ET, or through the LCD display on the Main Display Module in the dash, using the 4C-8195 service tool.
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The intake manifold air pressure (or boost pressure) sensor (1) is installed in the top left of the cylinder head and behind the HEUI pump.
The intake manifold air temperature sensor (2) is installed in the top of the intake manifold, to the left of the intake manifold air pressure sensor.
Ether is injected into the intake air through the ether aid injection tube (3), which is installed on top of the intake manifold. The ether injection strategy will be discussed later in this
presentation.
The crank-without-inject feature (4) is located above the intake manifold air pressure sensor.
The crank-without-inject feature is attached to the large wiring harness with wire ties.
Removing the end plug from the "Crank-Without-Inject" connector and inserting the attached alternate plug will electronically disable the fuel injectors. No fuel will be injected into the cylinders in this mode. This allows the engine to be cranked using the starter, without the engine starting.
The status of the intake manifold air pressure sensor, the intake manifold air temperature sensor, and the "Crank-Without-Inject" feature may be viewed using Cat ET, or through the LCD display on the Main Display Module in the dash, using the 4C-8195 service tool.
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The atmospheric pressure sensor (5) is installed in the top left of the cylinder head, behind the intake manifold air pressure sensor. The atmospheric pressure sensor measures the ambient air pressure and provides that information to the Engine ECM.
The status of the atmospheric pressure sensor may be viewed using Cat ET, or through the LCD display on the Main Display Module in the dash, using the 4C-8195 service tool.
NOTE: The signal from the atmospheric pressure sensor is used by the Engine ECM to calculate a number of pressure measurements. The signal from the sensor is compared to the signal from the other engine pressure sensors to determine the following:
• ambient (absolute) pressure is the atmospheric pressure
• boost pressure is determined by comparing the atmospheric pressure (sensor) to the intake manifold pressure (sensor)
• engine oil (gage) pressure is determined by comparing the atmospheric pressure (sensor) to the engine oil pressure (sensor)
• air filter restriction is determined by comparing the atmospheric pressure (sensor) to the turbo inlet pressure (sensor)
• fuel (gage) pressure is determined by comparing the atmospheric pressure (sensor) to the fuel pressure (sensor)
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Also, when the engine is started, the Engine ECM uses the signal from the atmospheric pressure sensor as a reference point for calibration of the other pressure sensors on the engine (if the key start switch is turned to ON for at least five seconds before the engine starts).
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The ether aid bottle (1) and the ether control solenoid (2) are mounted on a bracket at the left rear of the engine compartment.
When the ether control solenoid is energized, ether is injected into the intake manifold to aid in starting the engine in cold weather.
The Engine ECM controls ether injection by monitoring the intake air temperature and the coolant temperature sensors. If the temperature of the engine coolant or the intake air is less than 0° C (32° F), and the engine speed is greater than 35 rpm, but less than 700 rpm (low idle speed), then ether injection will be activated. Once the engine starts and the low idle speed is reached, the Engine ECM then looks to the ether injection map (contained in the engine software) to determine how long and how often to provide ether injection. This strategy helps meet emissions regulations by eliminating white smoke when the engine is first started.
The status of the ether control solenoid may be viewed using Cat ET, or through the LCD display on the Main Display Module in the dash, using the 4C-8195 service tool.
NOTE: There is no inlet air heater used in the C9 ACERT® engine for the D6T.
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The air cooled A4 Engine ECM (1) is located at the left rear of the engine, above the starter (2).
The Engine ECM and its software (flash file) are the main components of the electronic engine control system. The ECM controls engine performance by determining fuel injection timing, limiting fuel, and also functions as the governor.
The Engine ECM receives signals from all the sensors and controls the engine through the output components, such as the IAP control valve and the fuel injector solenoids. The Engine ECM also receives commands from the Machine ECM for various machine strategies, such as the Controlled Throttle Shifting strategy used during transmission shifts. The Engine ECM has the ability to communicate through the CAT Data Link with a Personal Computer (PC) using the Cat Electronic Technician (ET). The Engine ECM also communicates through the Controller Area Network (CAN) Data Link with the Machine ECM.
The J1/P1 connector (3) for the Engine ECM is a 70 pin connector and it connects the engine wiring harness to the ECM.
The J2/P2 connector (4) is a 120 pin connector and it connects the Engine ECM to the machine wiring harness.
The timing probe cable connector (5),(not visible in the illustration above), is fastened to the J2/P2 wiring harness, above the Engine ECM.
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The engine oil pressure sensor (1) is located ahead of the Engine ECM. The difference in pressure between the atmospheric pressure (sensor) and the engine oil pressure (sensor) is the engine oil (gage) pressure.
An engine oil pressure test port (2) is located above the engine oil pressure sensor.
Engine oil pressure varies with engine speed. Oil pressure can be read as absolute pressure or as gage pressure using Cat ET Low oil pressure threshold calculations are programmed into the Engine ECM. As long as oil pressure stays above these thresholds, the ECM reads adequate oil pressure. If engine oil pressure decreases below these thresholds, the following occurs:
• An event is generated and logged in the permanent ECM memory.
• A Level 3 Warning (alert indicator, action lamp, and alarm) is generated by the Caterpillar Monitoring System.
The status of the engine oil pressure sensor may be viewed using Cat ET, or through the LCD display on the Main Display Module in the dash, using the 4C-8195 service tool.
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The crankcase breather (3) is mounted to the left side of the engine block, forward of the Engine ECM. Fumes are directed from the valve cover to the breather through the large molded rubber hose (4). The fumes are vented at the left front of the tractor, beneath the radiator, through the flexible rubber hose (5).
The turbo inlet pressure sensor (1) is installed in the tube at the outlet of the air filter canister.
Turbo inlet air pressure sensor readings are used to determine air filter restriction. The Engine ECM compares the signal from the turbo inlet air pressure sensor to the signal from the
atmospheric air pressure sensor and calculates the difference. If the pressure differential is too high, it will cause the engine to derate.
The engine coolant temperature sensor (2) is installed in the top of the cylinder head and is located at the front center of the engine, immediately forward of the valve cover. It is a two-wire, resistive type (passive) temperature sensor.
The status of the turbo inlet pressure sensor and the engine coolant temperature sensor may be viewed using Cat ET, or through the LCD display on the Main Display Module in the dash, using the 4C-8195 service tool.
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The coolant (S•O•S) sampling port (1) is installed in the steel tube that directs water from the the temperature regulator (thermostat) housing (2) to the radiator. It is located at the right front of the engine and is accessible through the right side engine compartment door.
The jacket water pump (3) is also located at the right front of the engine, below the regulator housing. The bypass tube (4) connects the regulator housing to the jacket water pump. A single regulator is contained in the housing. When the coolant is cold the regulator is closed and the coolant is diverted from the cylinder head back to the jacket water pump through the bypass tube. When the coolant warms sufficiently, the regulator opens and the coolant is then directed to the radiator before returning to the jacket water pump. The jacket water pump forces coolant through the engine oil cooler and the power train oil cooler before it enters the engine block and cylinder head.
NOTE: Coolant samples should be taken only when the engine is at operating temperature and the coolant is circulating through the entire system. Always use a clean, lint-free towel to clean the test port prior to taking a fluid sample and replace the protective cap after a fluid sample has been taken. This will prevent damage to the test port and reduce the chance of introducing contamination into future fluid samples.
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The turbocharger (1) on the C9 ACERT® engine uses a standard mechanical wastegate (2).
The wastegate acts as a bypass valve for exhaust gasses to the turbine, which limits turbocharger rpm thereby limiting boost pressure.
The wastegate is operated by a pressure line (3) that connects the compressor side of the turbocharger to the piston mechanism of the wastegate. When the intake air (boost) pressure reaches the actuation pressure of the wastegate, the piston forces the linkage down, opening the wastegate. When the wastegate opens it allows some of the exhaust gasses to bypass the turbine side of the turbocharger limiting boost pressure, which in turn, limits the maximum engine cylinder pressure.
The turbocharger bearings are lubricated with cooled engine oil. The engine oil is directed to the bearings through the hard steel tube (lube line) (4).
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The alternator (1) is mounted at the lower right front of the engine and is accessible through the right side engine compartment door.
The engine oil filter (2) is located to the rear of the alternator.
The engine oil cooler (6) is an oil-to-water type cooler and is internal to the engine block. It is located behind the engine oil filter.
The engine oil sampling (S•O•S) port (3) is installed in the side of the engine block, to the rear of the engine oil filter. The sampling port is positioned upstream of the flow of oil to the filter.
Also shown above is the engine oil supply line (4) to the demand fan control manifold and the turbocharger lube oil supply line (5).
Below and to the rear of the engine oil cooler is the oil-to-water type power train oil cooler (7), which is in series to the engine oil cooler.
NOTE: Engine oil samples should be taken only when the engine is at operating temperature and the engine oil is circulating through the entire system. Always clean the test port prior to taking an oil sample and replace the protective cap after an oil sample has been taken. This will prevent damage to the test port and reduce the chance of contaminating future oil samples.
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The fuel pressure regulator (1) is located at the rear of the cylinder head. It is an in-line check valve that is upstream of the fuel line hose fitting (2) that returns unburned fuel to the fuel tank.
The fuel pressure regulator maintains a fuel system pressure between 455 and 579kPa (66-84psi).
The fuel pressure sensor (3) is installed in a "Tee" fitting, upstream from the fuel pressure regulator.
The status of the fuel pressure sensor may be viewed using Cat ET, or through the LCD display on the Main Display Module in the dash, using the 4C-8195 service tool.
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An engine prelube system is available as an attachment for the D6T Track-type Tractor.
The engine prelube pump (1) is driven by an electric motor (2). (The prelube pump is no longer driven by the starter motor.) The engine prelube pump is mounted to the lower right side of the engine, toward the front, as shown above.
The engine prelube pump draws engine oil through a hose (3) that connects to a fitting at the engine oil drain valve. The engine oil drain valve is located at the bottom left side of the engine oil pan.
A bracket (4) mounted to the inside of the right frame rail anchors the hose (5) that delivers the oil from the prelube pump to the engine block. This hose connects to a fitting at the engine oil cooler. The prelube timer and relay (6) is mounted to a bracket at the upper rear of the engine compartment.
The engine prelube system ensures there is sufficient oil pressure,30 kPa (4.4 psi), throughout the engine oil system before allowing the starter to crank the engine. This prelube system helps prevent premature wear of critical engine components.
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The serviceman can override the engine prelube system by turning the key start switch to the START position, then cycling the key start switch to the OFF position and back to the START position again within one second. This will allow the starter to engage without cycling the engine prelube pump.
NOTE: Can not be used on machines equipped with VPAT.
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The Quick-Evac Oil Change system for engine oil and power train oil is available as an attachment for the D6T. This system allows the oil from either system to be quickly drained and refilled through the same connections.
The quick-disconnect couplings for this system are located at the front left side of the engine compartment opening, near the top, and may be accessed by opening the left side engine compartment door.
The outer coupling (1) is for engine oil and it is connected to a hose (2) that runs to a fitting on the oil pan drain (3).
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Fuel System
Fuel is drawn from the fuel tank through the 10 micron primary fuel filter and water separator by a gear-type fuel transfer pump. The fuel transfer pump is mounted to the rear of the HEUI pump. The fuel transfer pump then produces the flow that pushes the fuel through the 2 micron secondary fuel filter.
The fuel then flows through a fuel line where it enters the front of the cylinder head. The fuel flows into the fuel gallery (inside the cylinder head), where it is made available to each of the six HEUI fuel injectors. Any excess fuel not injected leaves the rear of the cylinder head and is directed to the fuel pressure regulator. The fuel pressure regulator is an in-line check valve.
The fuel pressure regulator maintains a fuel system pressure of approximately 518 kPa (75 psi) between the fuel transfer pump and the fuel pressure regulator.
From the fuel pressure regulator, the excess fuel flow returns to the fuel tank. The ratio of fuel used for combustion and fuel returned to tank is approximately 3:1 (i.e. four times the volume required for combustion is supplied to the system for combustion and for injector cooling and lubrication purposes).